Will these mount directly to my existing mirror brackets?

These use factory mounting points, so they bolt straight onto OEM bracket locations with no drilling or modification needed.

Do I need to splice into my truck's wiring, or do these plug in?

These are designed to work with existing factory wiring harnesses. Your truck's power window/mirror circuit should supply power directly — no custom harness required.

Will the heated mirrors stay on automatically in winter?

Heated function activates through your truck's climate or accessory switch system depending on your model year. Refer to your vehicle's owner manual or wiring diagram for activation details.